In surgeries using a stereoscopic microscope, for example in the field of ophthalmology, neurosurgery, otology, etc., usually microscopes with a weak magnification are used. They have separate beam paths in order to make possible a stereoscopic viewing of the surgery field by the surgeon. Ocular systems are thereby utilized, each of which include an ocular tube. Furthermore, one common lens is usually used for both beam paths, in which a common collective lens is provided in most cases.
Diverging beams enter the lens in such a microscope, which beams are guided parallel through the lens systems and are directed to the magnification changer. The beams exit from the changer again in the form of parallel beams and are fed to the respective ocular system or ocular tube.
In the case of common stereoscopic microscopes suited for surgical purposes, it may be necessary to provide additional optic elements between the lens and the magnification changer or between the magnification changer and the ocular system, for example, beam splitters for optic recording devices or for co-observer systems. The use of this additional element results in a considerable increase of the structural length of the microscope, which is undesired both for technical use reasons and also for optic reasons. The structural length of the microscope is limited in technical use respects since the surgeon must carry out the surgery and at the same time also must watch same through the microscope. With respect to optic reasons, it is always desirable to keep the size of an optic device as small as possible, since an increase of the structural length results in a limitation of the optic field of vision and in addition is negatived by the loss of light.
The limitation of the field of vision is particularly disadvantageous for surgeries on the vitreous body of an eye or rather in the vitreous body area, since it is not possible or only possible under considerable difficulties to overlook the entire area subject to surgery. It is therefore desirable to expand the field of vision angle as much as possible, for example up to a value of 150.degree..
A further problem occurring in such stereoscopic microscopes results when the microscope is supposed to be used with an in-between image. An in-between image becomes necessary when, for example, the retina or the vitreous body area of the eye of the patient is supposed to be viewed. A collecting system in the form of a contact glass or a lens is in such a case usually applied onto or in front of the patient's eye. The optic system of the eye and the contact glass or the supplementary lens produce thereby a true image of the retina or of a plane of the vitreous body area. The true image is behind the contact glass or rather the supplementary lens and is used when the microscope is adjusted for focusing. Due to the optic relationships, this true image appears inverted and interchanged with respect to the sides. The interchanging of sides results in an inverse stereoscopic effect, which in turn causes the surgeon to recognize the foreground or the background of the stereoscopic image interchanged.
In order to overcome this interchanging of the stereoscopic effect and in order to reproduce the image in a correct manner, it is necessary, aside from the image inversion, to also carry out a change of the beam paths, namely, an interchanging of the right and the left beam path in the area of the microscope European A1-193 818 (which corresponds to U.S. Pat. No. 4,710,000) describes a stereomicroscope, in which the stereoscopic inversion and the image inversion is overcome by means of a prism arrangement or a prism system. However, this known prism system proves to be disadvantageous in some cases because of its size, with the size not only influencing the outside dimensions of the microscope, but also the length of the optic path. By extending the optic path, limitations of the field of vision and undesired light losses result in turn.
German OS 36 15 842 (which corresponds to U.S. Pat. No. 4,723,842) also discloses a prismatic intermediate assembly which is relatively large and consequently has the disadvantages known from the above-mentioned EP-A1-193 818.
The Book Naumann-Schroeder "Bauelemente der Optik", Hanser Verlag, discloses various prism systems for image inversion and for lateral shifting, which in general show the possibility for use of prisms.
The basic purpose of the invention is to provide a prism system or rather a stereoscopic microscope of the above-mentioned type, which with a simple design, a small size and high performance can avoid the disadvantages of the state of the art and can be manufactured inexpensively.
The invention provides a prism system, for a stereoscopic microscope having a plurality of deflecting surfaces each deflecting a right or left beam path by 90.degree., wherein four reflecting surfaces are provided in each beam path, wherein two of the surfaces in each beam path are each a reflection surface arranged in a plane parallel with respect to the optic longitudinal axis of the microscope, and wherein the two other surfaces are respectively inlet and outlet surfaces and are inclined at 45.degree. with respect to the optic longitudinal axis and at 90.degree. with respect to one another.
The inventive prism system is distinguished by a number of considerable advantages. By using four reflecting surfaces in each beam path, it is possible to guide the individual beams of the right or left beam path independently from one another in an exact manner so that on the one hand the inverted stereoscopic effect is removed and on the other hand an image inversion is carried out. With the separation into reflection surfaces and inlet or outlet surfaces, it is possible to arrange the individual surfaces separately from one another so that as a whole a design is created which, with the smallest structural dimensions, assures the highest degree of optic efficiency. Since the inlet or outlet surfaces are each inclined at 45.degree. with respect to the optic longitudinal axis and define an angle of 90.degree. with respect to one another, it is possible, while maintaining the same optic direction of the entering and exiting light beams of the prism system, for a narrow spacial association of the inlet and outlet surfaces to occur.
A particularly advantageous development of the invention provides that the surfaces arranged in planes parallel with respect to the optic longitudinal axis each define an angle of 90.degree. with respect to one another. Thus, it is possible to design the entire prism system with respect to its outside dimensions substantially square or rectangularly, with the base of the square or rectangle being able to be adjusted in a simple manner to the structural demands of the microscope. Since the right and the left beam path is guided parallel to the base of the rectangle or square, a definitely low structural height can be achieved, which proves to be particularly advantageous with respect to the entire construction of the microscope, since the entire length of the microscope must only be increased insignificantly in order to store the inventive prism system.
The reflecting surfaces are in a further advantageous development of the invention each constructed as hypotenuse surfaces of a rectangular prism member. This development has the advantage that the reflection of the light beam occurs inside of the prism member and that the light beams are not again broken when entering or exiting the prism member. A further advantage of this development lies in both the manufacture and also the assembly operations of the prism system being able to be significantly simplified.
Furthermore, it can be advantageous when the prism member includes an inlet surface of the one beam path on the prism member having the outlet surface of the other beam path, with both surfaces adjoining one another. Two prism members are in this development united to form a cube or cubical-shaped element, so that a particularly good utilization of the available spacial relationships is possible. A further advantage lies in the inlet or outlet surface being protected against damage, since these are covered by the respectively adjacent prism member.
Furthermore, it can be advantageous to arrange the prism members having the reflection surfaces each resting against one another or designing these so that they rest on the adjoining prism members including the inlet surface or the outlet surface. Since these prism members, which have the reflection surfaces, are arranged such that the reflection surfaces are on the outer periphery of the prism system, it is possible to significantly minimize the dimensions of the entire arrangement. It can thereby be furthermore advantageous to construct two of the prism members in one piece in each beam path. Loss of light during the entry or exit into the prism member medium is avoided by this measure. Furthermore, it is also possible to construct these prism members in one piece with the adjoining prism members having the inlet or outlet surface, so that the entire prism arrangement of the inventive prism system can be built of only two individual members. Such a development is particularly advantageous also in view of possible disadjustments, since individual adjustment of the individual reflection surfaces during installation into the microscope is no longer needed.
The reflecting surfaces can be either of the minor type with a reflecting coating, or, by selecting suitable materials of a total reflection type. Those of ordinary skill in the optic art are thoroughly familiar with conventional reflecting coatings and with conventional principles of material selection to effect total reflection, and thus those principles are not, in and of themselves, disclosed herein in detail. The specific materials selected to effect total reflection would depend on the wavelengths to be used, the structural dimensions, and the required optic qualities.
The purpose is attained with respect to the stereoscopic microscope by providing a prism system in an area of the microscope which includes two parallel beam paths. This development of the microscope has the advantage that no additional measures are needed for deflecting the beam path, since the already provided parallel beam paths can be used directly for transmission through the prism system.
The inventive prism system can be arranged in the inventive microscope between a collective lens, which is provided in the area of the lens device, and a magnification changer, which is provided in beam direction after the lens. However, it is also possible to provide the prism system between the ocular arrangement and the magnification changer. Thus, it is inventively particularly advantageous that the prism system can be inserted at any desired area of the microscope anywhere where parallel beam paths exist. Thus, it is possible to use the inventive prism system in connection with conventional microscope developments without requiring conversions or changes to the microscope.
A particularly advantageous further development of the inventive microscope is that the prism system, while maintaining the normal function of the microscope, can be removed from the beam path of same. The prism system can be moved or tilted, such that its movement is effected in the X- or Y-direction with respect to the optic axis of the microscope. This microscope development permits a quick change between a normal viewing through the stereoscopic microscope and a viewing of the surgery field using the inventive inverting prism system. Since no conversions of the microscope are needed in the inventive microscope for removing the prism system, the change can also be carried out quickly and easily by an unschooled operator. Furthermore, it has proven to be advantageous that the inventive prism system is very small, so that both the space needed for the change of the viewing manner can be dimensioned very small and also the required forces can be minimized. The latter is particularly important when the microscope, during surgery, must be held vibration-free on the eye of a patient. A further advantage is that in the inventive microscope upon removal of the inventive prism system, the normal viewing manner remains uninfluenced by the microscope, since the parallel beam paths can, upon removal of the prism system, continue to be guided parallel unhindered.